Comparison of Methods for the Mitigation of Spoofing Attacks in a Vector Tracking Based Software Receiver Architecture

In recent years, much work has been done to enable GNSS receivers to detect, recover from, and mitigate spoofing threats. This work focuses on the ability of a vector-based receiver to mitigate spoofing signals and maintain optimal performance after having recovered the authentic solution and continuing to operate in a known spoofing environment. One common method of continued spoofing mitigation is Successive Interference Cancelation (SIC) where the deterministic nature of the spoofed signal is exploited to estimate and remove the signal from the data stream. SIC relies on the ability of the receiver to have an accurate spoofer state estimate. If the spoofed signal overlaps with the true signal in the cross-ambiguity function (CAF), the correlation with both signals will provide inaccuracies in the spoofed signal estimates that can prevent SIC from fully removing the spoofed signal. Another common option is using beamforming techniques with an antenna array to mitigate the spoofing signal. This work introduces a combination and comparison of SIC and beamforming techniques for spoofing mitigation. The combined algorithm digitally nulls the authentic signal to estimate the spoofer states, removes the spoofer signal from the data stream with SIC, and then digitally beam steers towards the authentic signal for optimal spatial gain in the direction of the tracked signal. The digital beamforming and deterministic nature of the spoofed signal allows for the combined algorithm to attenuate the spoofer while simultaneously maximizing the authentic signal. The algorithm is deterministic and can operate through spoofing interactions in the CAF including attempted full recaptures. The SIC, null steering, and the combination algorithms are all compared in a signal level spoofing simulation to test the ability of a receiver to provide accurate measurements through interactions between the spoofer and authentic signals.